Removing cadmium from zinc ore.



G. RIGG.

REMOVING CADMIUM FROM ZINC ORE. APPLICATION FILED JULY 27. 1915.

1,161,886. Patented Nov. 30, 1915.

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TO CON 05 N85 6;

ro STATES PATENT orrIcE.

GILBERT RIGG, OF PALMERTON, PENNSYLVANIA, ASSIGNOR TO THE NEW JERSEY ZINC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

REMOVING CADMIUM FROM ZINC ORE.

Application filed July 27, 1915.

To all whom it may concern:

Be it known that I, (.irlLBERT Rico, :1. subject of the King of Great Britain. residing at Palmerton, Carboncounty. State of Pennsylvania. have invented certain new and useful Improvements in Removing Cadmium from Zinc Ore; and I do hereby declare the following to be a full. clear. and exact description of the invention, such as will e'n-' able others skilled in the art to which it appertains to make and use the same.

The present invention relates to the re moval of cadmium from zinc ore; for the purpose of recovering the cadmium and also for the purpose of obtaining a zinc ore product which is substantially devoid of cadmium and which can therefore be used in the manufacture of spelter in which cadmium is substantially absent.

In the accompanying drawing. I have shown. in general outline..a vertical section of apparatus utilizable tor the practice of the invention.

In carrying out the inventioin-I preferably make use of a down-draft through the cadmium-containing roasted or naturally oxidized zinc ore treated. The bed of ore is located upon a suitable supporting grate surface. either of the stationaryor traveling type. within a furnace structure wherein provision is made for effecting a downdraft through the charge.

In one form or modification of the invention. a layer of coal is placed on topof the layer of ore. This layer of coal is then ignited and a sufficient supply of air is drawn through the coal'and the charge to bring the charge to the reacting temperature for cad: I

mium reduction. The supply of air is then materially modified so that the reaction temperature referred to shall nou be exceeded within the mass. except to the extent unavoidable at the surfaces of contact between the solid fuel and the zinc ore. Under these circumstances. the carbon monoxid generated reduces the cadmium oxid and the released cadmium is carried off with the issuing gases. in a vaporous'condition. either as a metal or as an oxid. or (if sulfur is present) as a snlfid. It is received in any suitable condenser in whiclrit may be recovered, in whole or in part. 1n combination form a stable deposit; as for instance, cad- Specification of Letters Patent.

Patented Nov. 30, 1915.

Serial No. 42,210.

mium oxid or cadmium sulfid. Substantially all of the zinc which may be reduced at the surfaces of contact between the coal and the ore is caught and retained in the lower portion of the charge. The temperature of the lower portion of the charge, how-' and ore.

Instead of superposing solid fuel upon the bed of zinc ore. igniting the fuel and drawing air downwardly through it and the ore. I may. in some instances. draw downwardly'throughthe ore an ignited mixture of air with producer gas or other fuel gas until the ore reaches the temperature of reduction of cadmium but not of zinc. The air is then cut off and the reducing gas is alone drawn through the ore. thereby reducing and expelling the cadmium. The necessary temperature is maintained within the ore by periodically adding air to the gas and drawing the ignited mixture through the ore. The heating up of the ore to the nec-' essary temperature, alternated with the passage of the reducing gas therethrough, may he proceeded with until the cadmium has been expelled. I

In the case of ores containing sulfur, such as roasted blende ores, there is a tendency forthe cadmium to combine with the sulfur and to form cadmium sulfid which is but slowly reducible by the gas. This can be compensated, in'all of the instances hereinbefore referred to, by repeatedly alternating the conditions in the furnace from reducing to oxidizing. thus converting any cadmium sulfid formed during a reducing period to cadmium oxid during an oxidizing period. The admium oxid thus formed is then readily reduced and expelled during the next succeeding reducing period.

\Yhile I prefer. as hereinbefore indicated, to place the fuel layer upon the ore and to employ a down-draft, the fuel layer may in some instances be placed below the ore layer and an updraft may be used. So also, the

igiiited mixture of producer gas and air, and the subsequent current of gas alone, may be passed upwardlyinstead of downwardly through the ore, although with lesser advantagei f It will be understood, of course, that the purpose of the invention is not onlylto recover the cadmium, for the uses which cadmium has in the arts, but also to remove it as an impurity from the zinc ores containing it, so that it may not reappear in and deteriorate the spelter obtainable from the zinc ores carrying it. The conditions of the practice permit both of these purposes to be effected without any substantial reduction and loss of zinc during the cadmium-expelling operation.

"hat I claim is: I 1. The method of removing cadmium from roasted or naturally oxidized zinc ore,

. which comprises superposing, the one upon the other, a layer of fuel and a layer of cadinium-containing zinc ore, igniting the fuel and passing a body of air through the fuel and then through the ore until the ore 1S raised to the reduction temperature of cadof the ore layer mium but not of zinc. and continuing the passage of air through tl e'fuel and ore, for

the removal of the cadmium, without substantial removal of the zinc; as described. 1

The method of removing cadmium substantially from roasted or naturally oxidized zincore,

which comprises superposing. the one upon the other, a layer of fuel and a layer of cadmium-containing zinc'oi'e, igniting the fuel and passing a body of air through the fuel and then through the ore until the ore is raised-to the reduction temperature of cad inium but not of zinc.

and continuing the passage of-air through the fuel and ore,

'al of the. cadmium,w1thout for the r'emo substantial removal of the zinc, the depth being made suflicient to catch and retain substantially all of the zinc which may have been reduced at the surfaces of contactof the layers offuel and.

oxidized zinc ore,

pelled with the cadmium described.

4:. The method of removing cadmium from roasted or naturally oxidized zinc ore, which comprises subjecting the ore to the reducing action of a down-draft of reducing gas passed through the charge at a temperature sufficiently high throughout the charge to reduceand volatilize the cadmium and permit its expulsion from the charge, and sufliciently low at the exit zone for the reducing gas, to permit the charge to catch and retain any zinc that might otherwise be expelled with the cadmium; substantiall as described. a

5. The method of removing cadmium substantially as from roasted or naturally oxidized zinc ore, j

which comprises subjecting the ore to the reducing action of a down-draft of reducing gas passed through the charge at a temperature sufficiently high throughout the charge to reduce and volatilize the cadmium and permit its expulsion from the charge, and sufficiently low at the. exit zone for the reducing gas, to permit the charge to catch and retain any zinc that might otherwise be expelled with the cadmium, the reducing gas being produced by the ignition and combustion of a layer of fuel superposed upon the zinc ore charge; substantially as described. i

6. The method of removing cadmium from roasted or naturally oxidized zinc ore, which comprises subjecting the ore to the reducing action of a down-draft of reducing gas at a temperature sufficient to reduce and volatilize the cadmium 'without expelling any substantial quantity of the zinc, the reducing gas beingproduced by the ignition andcombustion of a layer of fuel superposed upon the zinc ore'cha-rge with the interposition of a layer of inert material; substantiallv as described.

' 7. In the art of removing cadmium from roasted or naturally oxidized zinc ore by the reducing action of a reducing gas at a temperature sufficient to reduce and volatilize the cadmium without expelling any substantial quantity of the zinc, the method of alternating reducing periods with oxidizing periods, so as tooxidize and render easily removable any cadmium sulfur compounds formed during the reducing periods; substantially as described.

In testimonywhereof I affix my signature, in presence of two witnesses.

, GILBERT RIGG lVitnesses JOHN C. PENNIE, M. BILL. 

